Method of working up coal tar pitch



3,490,586 METHOD OF WORKING UP COAL TAR PITCH Leopold A. Jaisle, Hamburg, Germany, assignor to Schill & Seilacher Chemische Fabrik, Hamburg, Germany No Drawing. Filed Aug. 22, 1966, Ser. No. 573,824 Int. Cl. C10c 3/02, 3/08, 1/20 US. Cl. 208-45 6 Claims ABSTRACT OF THE DISCLOSURE This invention is drawn to the process for treating coal tar pitch at 180-380 C. with a petroleum derivative having a boiling point of between 250-450 C. and recovering the insoluble components.

Coal tar pitch is the residue which remains behind when coke tar is distilled when the tar is distilled at atmospheric pressure up to about 360 C. A crude coal tar pitch has a normal softening point of about 44 to 49 KS. and, as a rule, a lower softening point of about 35 KS.

A method is known for working up coal tar pitch by treating it with various solvents boiling up to 250 C., e.g., by treating it with solvent naphtha, benzol, toluol, alcohol, ketones, glycols, etc. Through this treatment, the coal tar pitch is decomposed into an insoluble residue and into components which are soluble in solvents.

It has now been found that various valuable components can be separated and obtained from the coal tar pitch if it is treated at elevated temperature with a fraction or solvent extract of petroleum, e.g., a furfurol extract, undissolved components separated, e.g., through decantation, sedimentation, or centrifugation, and the solution worked up by distillation. Preferably the fraction or solvent extract of petroleum has a boiling point between about 250 and 450 C.

It has further been found that such fractions or extracts of petroleum, which contain predominantly aromatic components, can be used with special success.

Preferably one to two parts of the fraction or extract of petroleum is used per part of coal tar pitch. The admixture of the two components is best carried out by heating them homogeneously at 180 to 370 C. The mixture can then be cooled and the undissolved components separated. The cooling is preferably undertaken in steps, whereby the solid components are separated in steps. In this manner the mixture can be cooled down to about 90 C., and in many cases to about 60 C., with continued separation of insoluble components.

The solution obtained after the separation of the insoluble components is preferably crack-distilled, in which case one can go up to a distillation temperature of about 450 C.

The insoluble components separated from the solution can be reconditioned further, e.g., by extracting with solvents. Fractions or extracts of petroleum can be used, for example, as such solvents. Those boiling at 250450 C. are suitable. The solutions obtained in this step can then be recovered in known manner.

A more exact study has shown that, by using the method of the invention, much valuable material can be obtained, which may also include substances which are reaction products of the extracting solvent and components of the coal tar pitch.

The undissolved soot-like components obtained as sediment after the solvent is separated contain almost all substances (contained in the coal tar pitch) which are soluble in toluol and insoluble in pyridine. These insoluble substances, in contrast to normal coal tar pitch (44/49 K.S.), do not melt homogeneously with bitumen in a quantity ratio of 1:1. The toluol-soluble substances ob- United States Patent 3,490,586 Patented Jan. 20, 1970 "ice tained from the pitch which are contained in the solution, on the other hand, can melt homogeneously with bitumen, without the melt separating into parts at 0 C. These homogeneous bitumen melts can be used, for example, for paints, protective materials for buildings, binding materials, etc.

The solutions obtained with the method according to the invention, upon distillation, give a residue containing components of petroleum and coal tar pitch, and a distillate, which boils between about 300 and 420 C. and is still fluid at 0 C. This distillate can be used as an additive for natural and synthetic elastomers (rubber, etc.) as well as a swelling agent for certain high-molecular substances.

Upon distillation at temperatures above ca. 370 C., the components which are soluble in toluol decompose during cracking. Up to ca. 420 C., oily substances of unknown composition distill 01f. Coke-like substances remain behind as a residue.

From extraction of the separated insoluble residues, a further residue is obtained which can be broken up and then used as filler in combination with binding agents. This residue can also be coked to electrode coke, for example.

The solutions obtained by extraction of the separated insoluble pitch residue, which are entirely or extensively miscible with toluol, can be used, for example, for the thermal replasticizing of old rubber. If necessary, they can be recovered by distillation or other separating methods.

EXAMPLE 1 1000 parts by weight. of coal tar pitch with a softening point of 44 to 49 KS. were heated homogeneously with 500 parts by weight of a petroleum extract having a specific weight of about 0.9000 at 100 C., the temperature being increased up to 180 C. After cooling, 500 parts by weight of a standardized heavy heating oil with a specific weight of ca. 0.960 at 15 C. were added and the mixture heated again up to 180 C. The mixture was then cooled to 65 C. and left standing for 24 hours.

About 1200 parts by weight of a solution was separated from the undissolved residue and distilled at atmospheric pressure up to a temperature of 420 C. About 900 parts by weight of a reddish to dark brown aromatic-rich oil boiling at 360 to 420 C. was obtained, which consisted essentially of coke-like bitumen.

The insoluble components obtained after separation of the solution were extracted by means of ligroin having a boiling range of to C. in a Soxhlet flask. The solid extraction residue could not be distilled but coked above 420 C. The solution obtained by the ligroin extraction was added to the solution obtained in the second step of the method of Example 1 after the ligroin was distilled off.

EXAMPLE 2 100 parts by weight of coal tar pitch with a softening point of 44 to 49 KS. were heated homogeneously in a closed vessel on the standpipe at about 375 C. with 100 parts by weight of petroleum extract having a boiling point of 300 to 450 C., 'which contained 65 to 70% by weight of naphthene aromatics.

Upon cooling of the mixture to 200 C., about 17 parts by weight of a sediment separated out, which consisted of 48 parts by weight of substances soluble in toluol and 46% by weight of substances not soluble in pyridine.

After this sediment was separated, the mixture was cooled further to C. In this case, only small amounts of a sediment settled out, which consisted of a mixture of substances insoluble in toluol-pyridine.

The solution separated from the sediment was further cooled to 90 C. Here, about 44 parts by weight of a 3 sediment separated,'consi'sting of substances quite soluble intoluol'; I i

The solution was'then cooled'to 65 C., whereupon about 24"parts by weight of sediment separated out, which consisted of"about 9 8% toluol-soluble substances.

These amounts of sediment of various compositions contained 20% by weight of substances soluble in ligroin.

The remaining solution was distilled at atmospheric pressure. In the boiling range of 270 to 360 C., 18% by weight of an oil with a specific weight of 0.892 at 50 C. was obtained; in the boiling range of 360 to 380 C., 26% by weight of an oil with a specific weight of 0.918 at 50 C.; in the boiling range of 380 to 410 C., 14% by weight of an oil with a specific weight of 0.935 at 50 C.; and in-'the boiling range of 410 to 420 C., 17% by Weight of an oil with a specific weight of 0.943 at 50 C. 25% by weight of a black partially charred distillation residue remained behind.

' 1" EXAMPLE '3 I200 parts by weight coal ,tar pitch with a softening point, of 44 to 49 K.S. were heated with constantstirring to 180 C.. with 400parts. by weight of petroleum extract having a specific weight of 0.901 at 100 C. and'a content of about 70% by weight of petroleum resins. The mixture was then cooled to 65 C. and left standing for 3.5 hours.

90.4 parts by weight of a sediment and 493 parts by weight of a solution were obtained. This solution was heated again to 120 C., cooled to 65 C. and left standing at this temperature for five hours. 71 parts by weight of fatty substances separated out. The solution separated from the solid substances was viscous and could be dis.- tilled. No more substances separated out from the solution after standing for a longer time.

EXAMPLE 4 100 parts by weight of the coal tar pitch described in the previous examples were five times extracted by boiling out with 100 parts by weight of motor oil with a specific weight of 0.870 at 15 C. The extracts were combined and cooled to 60 C. About 26 parts by weight (26% weight of the coal tar pitch used) remained in solution. The extraction residue consisted of substances soluble in toluol and insoluble in pyridine.

These four examples demonstrate the progress according to the invention compared with the direct distillation of a mixture of petroleum extract with coal tar pitch in which case a considerably larger amount of coke-like distillation residue is obtained than with the method according to the present invention.

Various modifications and equivalents will be apparent to one skilled in the art and may be made in the method 4 of the present invention without departing from the spirit or scope thereof.

1. A'method for recovering a substance from coal tar pitch which comprises'heating'said pitch together with a derivative of petroleum at a temperature of about 180 to about 380 C., cooling the resultant solution to a temperature no greater than about 60 C., and separating the insoluble constituents, said petroleum derivative .having a boiling point of about 250 to about 450 C. and being selected from the group consisting of a pertoleum fraction containing a substantial proportion of unsaturated compounds and a petroleum extract containing a substantial proportion of aromatic compounds.

2. A method according to claim 1 wherein said petroleum derivative is a petroleum fraction containing a substantial proportion of unsaturated compounds.

- 3. A'method according to claim 1 wherein saidpetroleum derivative is-a petroleum fraction containing a substantial proportion of aromatic compounds.

' '4. A 'method' according to claim 1 wherein the separated solution is subsequently distilled at temperatures up to about 450'C."to produce 'coal tar pitch derivatives.

'5. Method according to claim 1, characterized by the fact that the insoluble components which have been separated from the solution are also extracted with a solvent, and the solution obtained in this way is further processed by distillation.

e 6. A method according to claim 5 characterized by the fact that the solvent utilized for extraction has a boiling point in the range of about 250 to about 450 C., and is selected from the group consisting of adistillate fraction of petroleum and a solvent extract of petroleum.

References Cited UNITED STATES PATENTS 1,275,778 8/1918 Sperr 106-278 1,355,099 10/ 1920 Weiss 208 1,553,641 9/1925 Sperr 20845 1,722,872 7/1929 Weindel 208-45 1,726,638 '9/ 1929 Weindel 208-45 2,060,447 11/1936 Schoenemann 208-45 2,936,282 5/1960 Paris et al. .20845 2,955,079 10/ 1960 Foley 208-45 3,372,045 3/1968 Baum 208-44 DELBERT E. GANTZ, Primary Examinerv VERONICA OKEEFE, Assistant Examiner U.S. Cl. X.R. 

